While I am not certain as to the actual source of the general Indy information used in the movie Jaws, Indy survivor Bob Gause, QM1, whose account of the half eaten sailor was told by Capt. Quint in the movie, states that his account was likely borrowed from the books Ordeal by Sea and Sharks!, both written by Thomas Helm back in the early 1960s. Ordeal by Sea was one of the first books to record the account of the Indy. Helm was a friend of Gause and included many of Bob's accounts in his books. Bob never identified the sailor publically, though he was a friend and knew who he was. As far as Quint identifying the sailor as, "Herbie Robinson from Cleveland, a baseball player and Boatswain's mate," there wasn't a crew member listed by that name aboard the Indy. It's also interesting, if you read the original novel Jaws, prior to the movie, the Indianapolis is never mentioned and Quint has minimal dialogue. The Indy story appears to have been added to enhance the script when they decided to make the movie. And enhance it, it did! Without question the segment featuring the Indy story garnered the movie it's blockbuster status....second to the shark, that is.